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Continuum electrostatic analysis of preferred solvation sites around proteins in solution
S Dennis1, C J Camacho, S Vajda
1Department of Biomedical Engineering, Boston University, Massachusetts 02215, USA.
Proteins
|February 3, 2000
Summary
Protein-water interactions are key to understanding solvation. This study reveals that conserved water sites in protein crystals closely match calculated free energy minima, suggesting protein-water interactions, not just crystal packing, determine water positions.
Area of Science:
- Biophysics
- Computational Chemistry
- Structural Biology
Background:
- Understanding water-protein interactions is crucial for molecular biology and drug design.
- Crystal structures provide static snapshots, but water behavior in solution is dynamic and less understood.
- Solvent binding sites are often conserved across homologous proteins, hinting at functional importance.
Purpose of the Study:
- To investigate the relationship between water positions observed in protein crystal structures and their preferred locations in solution.
- To determine the extent to which protein-water interactions, versus crystal packing, dictate the occupancy of specific water binding sites.
- To correlate calculated water residence times with experimental data.
Main Methods:
- Solving the Poisson-Boltzmann equation to calculate electrostatic fields.
- Mapping the free energy surface of water by moving an explicit water molecule around T4 lysozyme.
- Analyzing conserved solvent binding sites from 18 crystallographically independent T4 lysozyme molecules.
- Comparing calculated free energy minima with experimentally observed ordered water positions.
Main Results:
- Most conserved and nonconserved water sites are within 1.3 Å of calculated free energy minima.
- Randomly placed water molecules require significantly larger displacements to reach a minimum.
- Calculated water residence times align well with nuclear magnetic resonance experimental data.
- Crystal packing can influence or even override intrinsic protein-water interactions for certain sites.
Conclusions:
- Solvation sites are significantly influenced by direct protein-water interactions, not solely by crystal packing.
- Conservation of water sites across different crystal structures is linked to stable protein-atom configurations.
- The study provides insights into the dynamic nature of water molecules around proteins in solution and their representation in crystal structures.